SUNDAY, June 19, 2005 (HealthDay News) -- Two high-tech brain scans and a new blood test can identify Alzheimer's-linked neurological changes years before actual symptoms arise, researchers reported Sunday.
Besides allowing individuals to begin drug therapy early and plan for the future, these early-detection tests might someday help those at risk take full advantage of preventive therapies.
"We already have medications coming down the pike that are going to change the course of the disease," explained William Thies, vice president of medical and scientific affairs at the Alzheimer's Association. "As those medications come online, there's going to be a tremendous need to identify Alzheimer's disease earlier and earlier."
Three studies outlining the new screening technologies were presented at the Alzheimer's Association International Conference on Prevention of Dementia, in Washington, D.C.
One study, led by research scientist Lisa Mosconi of New York University's Center for Brain Health, used positron emission tomography (PET) scans hooked up to a specially designed, MRI-linked computer program. That program automatically tracks glucose metabolism in an area of the brain called the hippocampus, a key memory center.
"If there's reduced [metabolic] activity there, you have cognitive problems, and are at high risk of developing Alzheimer's," Mosconi explained. The technology grew out of the work of the center's director, Mony de Leon, whose team first discovered hippocampal shrinkage to be a hallmark of Alzheimer's disease.
Using this computerized scanning technology, the NYU researchers followed 53 healthy people between 54 and 80 years of age for between 10 and 24 years in a first-of-its-kind, longitudinal study. Participants received PET scans at the beginning of the study and then at the three- and seven-year mark.
Six of the participants did go on to develop Alzheimer's disease, the researchers reported.
According to Mosconi, reductions in hippocampal metabolism as measured by the PET/MRI technology accurately predicted who developed either mild cognitive impairment or Alzheimer's disease. And those predictions came an average of nine years before the onset of symptoms, she said.
"This is the first study that really follows subjects from normal age until the start of Alzheimer's," Mosconi pointed out. "Before this, we didn't have any indicators or biomarkers, and now we do. Now we can finally know what to look for and examine this further in clinical research."
Thies applauded the NYU effort, stressing that a longitudinal study of this type remains the "gold standard" of scientific research. Any technology able to measure brain metabolism is an important advance, he added, since these metabolic changes lie at the heart of Alzheimer's pathology.
In a second study, British researchers at University College London used another imaging technology called magnetic resonance spectroscopy (MRS), an MRI-type scan that examines brain biochemical activity instead of brain structure.
They ran MRS scans on a group of healthy individuals carrying a gene that strongly predisposes them to Alzheimer's later in life. The scans were calibrated to pick up levels of two neurochemicals -- N-acetyl aspartate (NAA) and myo-inositol (MI) -- which typically are altered in Alzheimer's patients.
As expected, brain scans of participants carrying the Alzheimer's gene showed abnormal levels of NAA and MI compared to noncarriers, even though they were relatively young and showed no detectable signs of cognitive decline.
In a third study, researchers at the Mayo Clinic in Jacksonville, Fla., may have developed a much more low-tech, inexpensive means of spotting the disease early -- a blood test.
A protein called beta-amyloid 40 (meaning it contains 40 amino acids) is ubiquitous in the blood and cerebrospinal fluid of healthy individuals, the researchers explained. However, Alzheimer's patients also carry abnormally high blood levels of a second protein, beta-amyloid 42.
In their study, the Mayo team drew blood samples from 563 healthy, elderly volunteers for between two to 12 years, and then tracked rates of dementia in the groups as they aged.
They found that participants with especially low beta-amyloid 40/42 ratios were at three times the risk of developing Alzheimer's, and developing it soon, compared to those with higher ratios.
According to Thies, the PET and MRI early detection methods are much further advanced in terms of their development than the blood-based screen. "But obviously, the blood screen is much cheaper, requires less machinery and fits much easier into the physician's routine," he said.
In the absence of effective treatments, however, does early detection really make sense?
Thies believes it does.
"First of all, the impact of the current medications we have is likely to be biggest in the early stages of the disease," he said. "And Alzheimer's disease is so dislocating for families -- knowing early allows you to plan better for the future in a number of ways."
Waiting until symptoms appear -- and competency is impaired -- may be too late, he said. "Then the affected individual is taken out of the mix, and the family is left trying to interpret what Dad or Mom would want."
Thies also believes that the decades-long push for effective, preventive therapies may soon bear fruit. The advent of powerful drugs that fight Alzheimer's will make early detection even more important than it is now, he said.
At the same time, advances in imaging technology are fueling this research boom, allowing scientists to locate and target exactly those areas of the brain most affected by the disease.
Thies described research into detection and treatment as "two trains going down parallel tracks. When one train gets ahead, it just becomes a powerful force pulling the other along."
For much more on Alzheimer's disease, visit the Alzheimer's Association.